Typical storages of a computer system includes a main storage, an extended storage and an input/output device.
JP-A-58-9276 which corresponds to U.S. Pat. No. 4,476,524 discloses an expanded storage (which is called a paging memory in the specification). In the system disclosed therein, high speed data transfer is attained between a main storage and the expanded storage by a conventional command or an input/output command.
JP-A-64-37636 which corresponds to U.S. patent application Ser. No. 079,314 discloses a method for imparting a storage area having a physical expanded storage split as an expanded storage for each VM in a virtual computer system in which a virtual machine (VM) which comprises a plurality of logical machines are generated on one computer and an operating system to run on each VM is permitted. However, the OS of each VM does not generate a virtual space for the expanded storage.
JP-A-60-122445 discloses a method for imparting a storage area having a physical main storage split as a main storage (virtual main storage) of the VM. According to the system disclosed therein, an address on the virtual space of the virtual main storage which a conventional command designates can be rapidly translated to a physical address. Further, according to the system disclosed therein, a channel can translate an address on the virtual main storage which a channel program of the OS designates to a physical address. In this manner, the conventional command of the VM and the input/output command which have the storage area having the physical main storage split can be rapidly executed.
The art disclosed in JP-A-64-37636 is very effective in rapidly effecting the data transfer between the virtual main storage of the VM which always resides on the physical main storage and the virtual expanded storage which always resides on the physical expanded storage. However, the following problems are encountered.
(a) The expanded storage of JP-A-64-37636 is used for paging. Accordingly, the OS on the VM is accessed only by the real address designation for the virtual expanded storage- The OS on the VM does not generate a virtual space for the virtual expanded storage. However, in order for a database system or an application program under the OS to use the expanded storage, it is desirable that the OS imparts a virtual space of the expanded storage to each program. Further, it is desirable that the data is directly transferred between the virtual space on the VM virtual storage and the virtual space on the virtual expanded storage. In this case, the translation information for translating an address (virtual ES address) on the virtual space on the virtual expanded storage to a real address (virtual physical ES address) on the virtual expanded storage may be prepared by the OS as a relocation table of the virtual main storage. The relocation table is provided not on the virtual expanded storage but on the virtual main storage because the main storage can be more rapidly accessed than the expanded storage is.
(b) Where the translation information for translating the virtual ES address to the virtual physical ES address is realized in the instruction processor as a relocation register, it is also desirable that the direct data transfer is effected between the virtual space of the VM virtual main storage and the virtual storage on the virtual expanded storage. The relocation table is provided not on the virtual main storage but as the register because the register can be more rapidly accessed than the main storage is.
(c) In JP-A-64-37636, the data transfer between the VM virtual main storage and the virtual expanded storage is effected by a conventional command other than the input/output command. However, it is desirable to effect the data transfer between the VM virtual main storage and the virtual expanded storage by the input/output command.
(d) It is desirable to enable the VM's to share the virtual expanded storage to enable sharing of data by the VM's.